Ancient people invented many unique things that are beyond the power of even modern engineers, who have in their arsenal the unlimited possibilities of computing and "smart" technologies. Take, for example, a refrigerator, the invention of which is in no way associated with ancient civilizations. But in vain, because it is known for certain that its prototype is the yachchals ("ice pits"), which were built by the Persians in the hot deserts.
They managed to produce and store ice without electricity, various coolants, and most of the elements found in modern refrigerators.
The unique design of a giant refrigerator, which could be used even in desert conditions, was developed by Persian engineers about 2, 4 thousand years ago. Although it is quite possible that people have made them before, no information about this has survived. Yakhchal ("ice pit") is an ancient type of evaporative cooler.
It is quite simple to make, so even the poorest people could make them at no extra cost. Despite the fact that only scrap materials and brute force were used, knowledge of the intricacies of technology was still required, since such structures, created in antiquity, can be considered the pinnacle of engineering.
To begin with, the deepest square-shaped hole was dug, the volume of which could reach 5 thousand cubic meters. m. Such gigantic areas were used for public storage, while the private facilities of the evaporative cooler were much more modest.
After that, the ground part was erected from adobe bricks, having a domed shape, the height of which could reach 18 meters. When it was strengthened, a special solution was used in the finishing work, which allowed it to maintain sub-zero temperatures and prevented evaporation even on the hottest days.
To create a thermos effect and avoid waterproofing, a sārooj solution was used, which includes clay, sand, ash, egg yolks, goat's hair, lime and ash in certain proportions. When the protective layer dried, the structure became absolutely waterproof and with low heat transfer.
And this is not surprising, because at the end of the construction, the walls at the base of the "ice pit" were more than 2 meters thick. According to centuries-old technology, towards the top, the walls became thinner and a hole was always left at the very top of the dome so that warm air could freely leave the cooler.
Remarkable:A wall was built next to large yachts on the southern side of the structure, oriented from east to west, while water was supplied to the cooler from the north side. This made it possible to create more shade, protecting the water from overheating during transportation at lunchtime, and the refrigerator itself was partially hidden from direct sunlight.
Most often, the yachts were filled with chopped ice, which was delivered from the mountainous areas of the northern territory, where the temperature is always below zero in winter. The rest of the time, people could be content only with water from the aqueducts, which at night also cooled quite well during transportation. Oddly enough, but in the desert at night the temperature drops to 0 degrees (and this is at a daytime temperature of + 50-70 above zero!).
Thick walls alone were not enough to keep the ice cool and keep it cool. As it turned out, the ancient inventors also used badgirs - mechanisms for catching the wind, which directed the air flow into the lower compartments of the yachts.
As it descended, the air was cooled by a huge mass of ice, as well as by cool air, which was stored inside a voluminous refrigerator. Thus, a natural ventilation system was created, since cold air currents displaced warm ones, keeping cool, constant temperature and fresh air.
Since it was not possible to avoid ice melting, the engineers also came up with systems for collecting and returning water to the "ice pit", where it was again frozen in separate containers. Most often, this ice was cut into pieces and sent to the homes of wealthy people and merchants who did not acquire such structures. There it was used to store food and drinking water, which was in deep wells. They, in turn, were part of the cooling system of all rooms - ancient air conditioners.
Interesting fact: Yakhchals are well preserved in Iran, Afghanistan and other parts of Western and Central Asia, where they have been successfully used for thousands of years. Now these monuments of ancient Persia are tourist attractions and part of the cultural heritage of these countries. Most of the "ice pits" are preserved in the province of Kerman (Iran), where you can see completely unique objects, like the double yachkal of Siryan, for example, which has no analogues anywhere on the planet.